The present invention relates generally to the field of radiopharmacy and more particularly to a system and method for in-process integrity test of a filter in a dispenser system.
Radioactive parenterals (or injectable medicine) are widely used for medical imaging, such as, for example, positron emission tomography (PET). PET scanning technique is commonly used in clinical medicine and biomedical research to create images of a living body in its active state. PET scanners can produce images that illustrate various biological processes and functions. In a PET scan, the patient is initially injected with a radioactive substance known as a “radioactive tracer” or “radiotracer” that can become involved in certain physiological processes in the patient's body. Typical positron-emitting radiotracers contain isotopes such as, for example, 11C, 13N, 15O and 18F. When positrons are emitted within the patient's body, they recombine with electrons in the neighboring tissues and become annihilated. The annihilation event typically results in a pair of gamma photons being released in opposite directions. One or more detector rings then detect these gamma photons, and the detection data are processed to reconstruct two-dimensional (2-D) or three-dimensional (3-D) tomographyic images.
Preparation of radiotracers is an important step for medical imaging (e.g., PET scans). Due to their radioactivity, radiotracers are preferably handled in automated dispenser systems. In such dispenser systems, before a vial is filled with a radiotracer having a specified radioactivity and volume, the radiotracer is typically flowed through a sterile filter to reduce bacteria and particulate content. A portion of a conventional radiotracer dispenser system is shown in FIG. 1. In this radiotracer dispenser system, a liquid radiotracer 10 is flowed from a bulk container (not shown), via a tube 103, a sterile filter 106 and another tube 104 before it eventually fills a vial 102. The tube 103 is coupled to the sterile filter 106's input side (12), and the tube 104 is coupled to the sterile filter 106's output side (14). The sterile filter 106 helps remove bacteria and/or particulate from the radiotracer 10.
During operation of a radiotracer dispenser system, the sterile filter therein has to undergo one or more integrity tests, for example, before and after a filling process. The integrity tests are performed to ensure the sterile filter meets specification and the filter membrane is intact during filtration. Conventionally, the integrity tests of sterile filters are carried out in special devices separate from a radiotracer dispenser system. That is, a sterile filter has to be manually removed from the dispenser system for an integrity test. This conventional approach poses a number of problems.
For example, instead of testing a sterile filter immediately after a radiotracer dispensing operation, it is desirable to wait until radioactivity of the radiotracer residue in the filter has decayed to a safe level. However, since a short-lived radiotracer has to be injected into a patient soon after it is dispensed, a delayed integrity test would be too late to prevent injection of a defective sample/batch. The only alternative, then, is for the personnel to remove the filter and start testing it immediately after a dispensing operation, thereby risking exposure to strong radiations.
In addition, it takes time for a sterile filter to be removed and tested elsewhere, and for a new filter to be installed. Therefore, with the conventional approach, it is impracticable to perform frequent integrity tests, and it is difficult to predict the remaining lifetime of a sterile filter. The useful life of a sterile filter is often conservatively estimated, after which time period the filter is tested for integrity. If the filter fails the integrity test, the radiotracer batch that has just been dispensed through this filter must be disqualified. Even if the filter passes the integrity test and still has some remaining useful life, it will be discarded.